O31-02 : Light-driven transmembrane H +, Na+ and Cl- pumping is mediated by three different rhodopsins in a marine flavobacterium
Posted On 20 10月 2014
1Atmosphere and Ocean Research Institute, The University of Tokyo, 2Massachusetts Institute of Technology, 3Division of Genomics and Bioenvironmental Science, Frontier Science Research Center, University of Miyazaki
Light-activated, ion-pumping rhodopsins are broadly distributed among many different bacteria and archaea inhabiting the photic zone of aquatic environments. Bacterial proton or sodium translocating rhodopsins can convert light energy into a chemiosmotic force that can be converted into cellular biochemical energy, and so represent a widespread alternative form of photoheterotrophy. Here we report the genome sequence of the marine flavobacterium Nonlabens marinus S1-08T. As a result, three different types of rhodopsins (NM-R1, NM-R2 and NM-R3) were found in the genome data of this strain. Functional analysis demonstrated that NM-R1 and NM-R2 are light-driven outward translocating H+ and Na+ pumps, respectively. On the other hand, the light-activated NM-R3 rhodopsin pumped Cl– ions into the cell, representing the first chloride pumping rhodopsin to be reported in a marine bacterium. Phylogenetic analysis revealed that NM-R3 belongs to a distinct phylogenetic lineage quite distant from archaeal inward Cl– pumping rhodopsins like halorhodopsin. In total, our data suggest that similar to haloarchaea, a considerable variety of rhodopsin types with different ion specificities have evolved in marine bacteria, with individual marine strains containing as many as three functionally different rhodopsins.